Gravity-actuated high-voltage switch



Oct. 1.8, 1949.. R P, ROETTER 2,485,170

' GRAVITY-ACTUATED HIGH-VOLTASIE SWITCH I Filed Nov. :50,v 1946 :inventor mtorneg Pnenfed oa.'1s,1949

GRAVITY-ACTUATED HIGH-VOLTAGE SWITCH O Robert P. Roetter, Westmont, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application November so, 1946, 'serial No. 713,195

claims. (ci. zoo-166) This invention relates to electrical switches and has for its principal object to provide an improved gravity-actuated switch, and one particularly characterized by the positive, non-bouncini` action of its contacts.

Another and important object of the present invention is to provide a simple, yet rugged, highvoltage switch and one wherein any arc-over which may occur is confined to areas on the switch which are remote from the active surfaces of its contacts, whereby the life of the switch is prolonged by obviating the pitting of its said contact surfaces.

Still another object of the present invention is to provide an inexpensive and reliable spring-less switch which shall be suitable for use in a safety system for preventing access to the interior of a high-voltage compartment so long as the power is The invention will be described in connection with the accompanying drawing wherein: Fig, 1 is a partial section, in side-elevation, taken on, the line I--I of Fig. 3, of a safety-systemincorporating a gravity-actuated switch within the invention, the switch being open; Fig. 2 is a similar view, with the switch contacts closed; Fig. 3 is a front elevational view taken on the -line III- III of Fig. 2; and Fig. 4 is a top plan view of the switch.

In the embodiment of the invention which .has been selected for illustration, I designates the vdoor of a high voltage compartment 2 of a radio ,transmitter or the like and 3 designates, generally, a gravity-actuated switch constructed in accordance with the principle of the invention and arranged (in a manner later described)`.to close upon opening the door I and to open upon closing of the said door.

The supporting structure for the switch comprises an inverted U-shape frame I which is secured, as by screws 5, tothe base 2a of the compartment 2, adjacent to the door I. A bracket 6 comprising two outwardly and downwardly inclined arms 6a, 6b which are secured as by screws 1 to the short (top) arm of the U, serve to support, on their underside, two parallelly arranged, inwardly inclined, downwardly extending porcelain or similar insulators 8, Ba which in turnr support a stationary switch-contact 8 having a curved, preferably cylindrical, contact surface 3a. The upper surfaces of the arms 6a and 6b of the bracket 6 carry two upwardly extending ilanges Illa and lob that serve as bearings for the fulcrum or axle II of a dependent switch arm I2 which, in the absence of any restraining torce, is

free to move vertically in the space between the two porcelain insulators 8 and 8a. This movable metal .arm I2 comprises a lever of the third class and carries a second or movable switch-oontact I2a adjacent to its lower or free end for engagement with the. stationary contact 8. The switch is thus normally biased by gravity to its closed position (as shown in Fig. 2) but is held open, when the door I is closed (as shown in Fig. 1), by the weight of the door I (or by the force of its latch, not shown) which is applied to the lever I2 through an adjustable bali-headed stop or arm I3 arranged intermediate the axle or fulcrum II and the movable contact or weight I2a.

It will be observed that the lever arm l2-is grounded both through its axle II and, by means of a braided copper strap I4, to the inverted U- shape metal frame 4. Thus, when the door or ing the lever I2 and its movable contact I2a that A the force of the lever is largely compressive on the insulators 8, A8a and the movable contact I2a is presented in wiping engagement to the stationary contact 9 at an angle of from not less than 5, nor more than 10, with respect to a line drawn tangent to the curved contact surface 9a at the point, or line of engagement. As indicated inFig. 2 of the drawing, the angle of engagement best calculated to prevent bouncing, and arcing due to bouncing, is approximately 61/2".

The movable contact I2a preferably comprises a flat surface, though it may be curved if the curvature is such as to cause it to engage the stationary contact-surface 9a along a line or point, rather than with a seating or nesting type of engagement. When, as inthe illustrated embodiment of the invention, the stationary contact comprises a cylindrical surface and the movable contact comprises a flat surface, which is presented at a small angle to the former, the electrical arc normally incident to the grounding of a live circuit will jump. from the leading side (instead of the bottom) of the cylindrical surface latotheleading edge llboftbe lever (instead of to the flat surface of the moving contact ila) and hence will not pit or otherwise mar the active surfaces of either one of the said contacts.

As previously pointed o ut, when the door I is closed it pushes the arm or stop i3 inwardly and hence lifts the lever l2 and breaksthevcontact between 9a and I2a. This stop I3 is preferably in the form of a screw and is placed near the center of motion, thus, only a small movement of the door i is needed to operate the switch and the door cannot be opened far enough to allow some one to insert his hand into the compartment 2 so long as the switch is ungrounded.

It will now be apparent that the present invention provides an improved non-bouncing highvoltage switch and capable of operating inde nitely without pitting the active surfaces of its a line drawn tangent to saidcurved surface at:

said point.

2. A switch in accordance with claim 1 and wherein said contacts are adapted to engage at an angle of approximately 6%".

3. A switch comprising in combination; two rigid contacts, one of said contacts having a curved surface and the other of said contacts having a substantially flat surface; a gravity biased actuating arm having one of said contacts mounted thereupon so that its path engages the other of said contacts contiguously; said contacts being in such relation that said pati meets said curved contact at a small angle with respect to the tangent of said curved contact at the point of contiguity, thus providing a wiping engagement with compressive force between both said contacts, said force being in an outward direction.

4. A combination in accordance with claim 3 with said contact angle being between 5 and l0.

5. A gravity biased switch comprising a movable arm pivoted about an axis in the form of a lever, an actuating arm between said axis and the free end of said lever, a substantially at rigid contact adjacent said free end, 'and a stationary arm having a rigid curved contact surface mounted at a point contiguous the path of movement of said flat contact, -said flat contact being disposed on said lever arm so that said path of movement i engages said curved contact at an angle of not less than 5 nor more than 10 with respect to a line drawn tangent to said curved surface at said point.

' ROBERT P. ROEI'I'ER.

REFERENCES CITED The following references are of' record in the 

